#include<iostream>
#include<vector>
#include<iomanip>
using namespace std;
const int N = 1e5 + 10;
int n;
double a, b;
struct Node {
	vector<int> ne;
	bool vis;
}node[N];
double memo[N];
double dfs(int x,double d)
{
    
    if(memo[x]!=0)
    {
        return memo[x];
    }
	if (node[x].vis == true)
	{
		return memo[x]= (d * node[x].ne[0]);
	}
	else {
		double d1 = 0;
		for (int i = 0; i < node[x].ne.size(); i++)
		{
			double p = dfs(node[x].ne[i], (d*(1+0.01*b)));
			memo[node[x].ne[i]]=p;
			d1+=p;
		}
		return memo[x]=d1;
	}
}
int main()
{
	cin >> n >> a >> b;
	for (int i = 0; i < n; i++)
	{
		int x;
		cin >> x;
		if (x == 0)
		{
			int y;
			cin >> y;
			node[i].vis = true;
			node[i].ne.push_back(y);
		}
		else {
			node[i].vis = false;
			while (x--)
			{
				int y;
				cin >> y;
				node[i].ne.push_back(y);
			}
		}
	}
	cout << fixed << setprecision(1) << dfs(0, a);
	return 0;
}